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Do the torque charts on Portland Bolt’s website apply to anchor bolts?
Question: Do torque charts for tensioning fasteners apply to anchor bolts?
Answer: The AISC Steel Construction Manual, 13th Edition has this to say about anchor rod nut installation.
“The majority of anchorage applications in buildings do not require special anchor rod nut installation procedures or pretension in the anchor rod. The anchor rod nuts should be “drawn down tight” as columns and bases are erected. This condition can be achieved by following the same practices as recommended for snug-tightened installation in steel-to-steel bolted joints in the RCSC Specification. That is, most anchor rod nuts can be installed using the full effort of an ironworker with an ordinary spud wrench.
When, in the judgment of the owner’s designated representative for design, the performance of the structure will be compromised by excessive elongation of the anchor rods under tensile loads, pretension may be required. Some examples of applications that may require pretension include structures that cantilever from concrete foundations, moment-resisting column bases with significant tensile forces in the anchor rods, or where load reversal might result in the progressive loosening of the nuts on the anchor rods.
When pretensioning of anchor rods is specified, care must be taken in the design of the column base and the embedment of the anchor rod. The shaft of the anchor rod must be free of bond to the encasing concrete so that the rod is free to elongate as it is pretensioned. Also, loss of pretension due to creep in the concrete must be taken into account. Although the design of pretensioned anchorage devices is beyond the scope of this manual, it should be noted that pretension should not be specified for anchorage devices that have not been properly designed and configured to be pretensioned.”
So, in a nutshell, what does this mean?
It means, that in normal circumstances, the normal effort of an ironworker with a regular spud wrench is sufficient to tighten the nuts on anchor bolts. In the event that special pretensioning is required, the design engineer should have carefully designed the anchor assembly specifically for that purpose and there should be detailed instructions so that the pretensioning is carried out properly.
Posted by Dane McKinnon
Phone: (503) 219-6991 Email: danem@portlandbolt.com
View other posts by Dane McKinnon
@Pyara Kamboj – Apologies, but Portland Bolt cannot make specific application recommendations like this. Additionally, we do not work with metric fasteners and are not familiar with Q345B material so are unable to help with this request.
March 4, 2013 at 9:00 amHi,
I would like to ask preferred Torque setting for 15 Meter mono pole foundation bolts Bolt Size is M36 and used Material is Q345B
Bolts are 1200 mm long and embedded in Concrete.
If needed I can share drawing.
Thanks in advance
Pyara Kamboj
March 3, 2013 at 11:02 am@S.K. Sampath – Apologies, but we do not have any application engineers on staff, you will need to contact one to get recommendations for pretensioning.
October 15, 2012 at 8:28 amWe have a solar thermal power project at Pokran Rajasthan India where foundfation bolts embedded in concrete is required to be pretensioned. Can you please suggest suitable method for acheiving this. We can send you the foundation drawing if you wish to see the complete details.
October 15, 2012 at 1:05 am